The Iranian authorities have said the nuclear agreement reached more than 10 years ago cannot be re-negotiated.

US President Donald Trump on Monday said that he decertified Iran’s compliance with a landmark nuclear agreement because he is ‘tired of being taken advantage of’, hinting pulling his government out of the 2015 pact with Tehran is a “very real possibility”.

"I feel strongly about what I did. I'm tired of being taken advantage of as a nation. We'll see what phase two is. Phase two might be positive. It might be very negative. Might be a total termination. That's a very real possibility. But it also could turn out to be very positive. We'll see what happens," he said.

Trump said that he was pleased that lately ‘the tone of the Iranian leaders was very modified’.

"And I was happy to see that. But I don't know if that means anything," he added.

He called the Iranians ‘great negotiators’ because "they negotiated a phenomenal deal for themselves, but a horrible deal for the United States".

Trump had on Friday announced that for now he will maintain the US participation in the nuclear agreement with Iran, but will back out if it isn't modified unilaterally by the US Congress or multilaterally in negotiations involving all the signatory nations.

Specifically, the President wishes to correct the "weak inspections" allowed in the accord, deal with Tehran's "ballistic rocket programme" and eliminate the "expiry dates" fixed on Iran's nuclear programme, which in some cases expire after as much as 10 to 25 years.

Trump urged the US Congress to pass an amendment to the law that marks "red lines", which, if they are crossed, would immediately bring back the sanctions that were lifted on Iran's nuclear programme by the agreement signed with France, the UK, Germany, China, Russia and Iran.

The Trump government will also try to reach a parallel accord with the signatory countries that deals with the expiry dates, the ballistic missile programme and the mechanisms for inspecting Iranian nuclear facilities.

The Iranian authorities have said the nuclear agreement reached more than 10 years ago cannot be re-negotiated and that the pact will be respected as long there is reciprocity from the signatory nations. They also asked for European efforts to impede the latest US strategy.